# std::match_results<BidirIt,Alloc>::length

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< cpp‎ | regex‎ | match results

difference_type length( size_type n = 0 ) const; |  | (since C++11)

Returns the length of the specified sub-match.

If n == 0, the length of the entire matched expression is returned.

If n > 0 && n < size(), the length of nth sub-match is returned.

if n >= size(), a length of the unmatched match is returned.

The call is equivalent to (*this)[n].length().

`ready()` must be true. Otherwise, the behavior is undefined.

### Parameters

n | - | integral number specifying which match to examine

### Return value

The length of the specified match or sub-match.

### Example

| This section is incomplete Reason: no example

### See also

operator[] | returns specified sub-match (public member function)
length | returns the length of the match (if any) (public member function of `std::sub_match<BidirIt>`)

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